raw sienna vs yellowish brown

raw sienna and yellowish brown both are nouns.

Word	Noun	Adjective	Verb	Adverb
raw sienna	Yes	No	No	No
yellowish brown	Yes	No	No	No

As nouns, raw sienna and yellowish brown are synonyms defined as:

Other synonyms of raw sienna include buff, caramel, caramel brown.

raw sienna (noun)	yellowish brown (noun)
a medium to dark tan color	a medium to dark tan color
a yellowish-brown pigment made from untreated sienna